In the United States alone, more than 32,000 people commit suicide each year and it is estimated that for every death by suicide there are 8-25 nonfatal suicide attempts. Given the clinical and public health significance of suicide, there is considerable interest in identifying proximal factors that increase the risk for suicide attempts and that determine the timing of suicide attempts among individuals who often report persistent suicidal ideation. Despite consistent findings of an elevated prevalence of alcohol use surrounding suicide attempts, little is known about whether acute alcohol use serves as a trigger to suicide attempts, or whether the effect of acute alcohol use on suicide attempt differs as a function of chronic alcohol use. Disentangling the effects of acute alcohol use and risk of injury according to an individual's usual consumption pattern is a matter of great public health interest, and there are known differences in psychological characteristics (e.g., mood disorders, previous treatment history) between those who attempt suicide with and without alcohol use disorders (AUD), as well as between individuals who drink alcohol (A+) and who do not drink alcohol (A-) prior to their attempt. However, little is known about differences on such factors between suicide attempters with AUD+ (who do or do not use alcohol immediately prior to their attempt), AUD- individuals who use alcohol before their attempt, and AUD- individuals who do not consume alcohol prior to their attempt. In the proposed exploratory/ developmental study (R21), we will examine the unique triggering role of acute alcohol use on suicide attempts as a function of an individual's baseline AUD status, and will also examine distal psychological characteristics of distinct groups of attempters characterized by acute and chronic alcohol use. To this end, we will employ a case-crossover design with a between-subject comparison, recruiting 150 individuals presenting for medical evaluation after a suicide attempt. The one-session assessment will comprise a diagnostic measure of AUD, a battery of questionnaires assessing psychological characteristics, and a standard interview assessing substance use and other time-varying proximal risk factors during the six hours prior to the suicide attempt, as well as during two matched controls periods. This exploratory/developmental study will provide preliminary data on the magnitude of the unique within-subject relation between acute alcohol use and attempt among individuals with and without AUD, and will aid in identifying distinguishing characteristics of groups of attempters characterized by different patterns of acute and chronic alcohol use. These preliminary data and effect sizes will be used to inform the development of a larger study. Gaining a better understanding of the triggering effects of acute alcohol use on suicide attempts among those with and without AUD, and identifying psychological characteristics of individuals with different acute and chronic alcohol use patterns will facilitate future identification and treatment of alcohol-related suicide attempts.